1. Field of the Invention
The invention relates generally to defibrillators and, more specifically, to an external defibrillator having a built-in test load feature.
2. Description of Related Art
Defibrillators are used to apply an electrical shock to a patient's heart in response to a life-threatening condition such as an arrhythmia or cardiac arrest. External, or transthoracic, defibrillators deliver a pulse through a pair of electrodes placed on the patient's chest or back by the attending medical personnel. As shown in FIG. 1 (Prior Art), a defibrillator 101 generally includes a controller 103 (such as a microprocessor) which controls the operation of an energy source 105, 107, 109 and an energy discharge switch 111 to deliver an electrical pulse to electrodes 113, 115 (sometimes referred to in the art as the "paddles"). The controller 103 receives a command through a user interface, "shock button," 117. The electrodes 115 are also used to provide patient-feedback 119, 121 to the controller 103. Defibrillator operational readiness and patient-related information may be monitored on a display 121. Particularly in portable defibrillators, the electrodes 115 are disposable, typically packaged having a conductive gel on the paddle faces to lower the electrical resistance between the electrodes and the patient 131 and an adhesive for holding the electrode paddles on the patient. Therefore, the paddles 115 are releasably attached to the defibrillator 101 via an electrode connector, or connector port, 113.
Before actual use of a defibrillator 101 where the patient 131 provides the load across the paddles 115, it is important, particularly in an emergency situation, for medical personnel to know that the defibrillator is fully functional. A variety of defibrillator test methods and apparatus have been developed. Separate test simulation units which plug into the electrode connector to simulate a patient feedback are used in defibrillator training. In U.S. Pat. Nos. 5,591,213 and 5,617,853 by Morgan, assigned to the common assignee of the present invention, patient simulation and analyzer circuits are built into a defibrillator. Neither provides the capability of testing through the actual electrode port itself, therefore leaving a critical component untested as to operability. In U.S. Pat. Nos. 5,611,815 and 5,662,690 by Cole et al., assigned to the common assignee of the present invention, such training mode circuitry simulates delivery of a shock without actually delivering the pulse to the electrodes. U.S. Pat. Nos. 5,645,571 and 5,797,969, assigned to SurVivaLink Corp., show built-in self-test systems; again, neither provides a capability of testing through the actual electrode port itself.
There is a need for a test load implementation scheme which automatically is activated when the defibrillator unit is not in use with a patient and which tests the ability of the unit actually to deliver a shock pulse through the electrode connector.